A new study by Edward Giovannucci, M.D., Sc.D., at the Harvard School of Public Health finds long-term coffee consumption may be associated with a reduced risk for endometrial cancer. The study appears in Cancer Epidemiology, Biomarkers & Prevention. Dr. Giovannucci says coffee is emerging as a protective agent in cancers that are linked to obesity, estrogen and insulin. In a press release, Dr. Giovannucci explained why the study was undertaken:

“Coffee has already been shown to be protective against diabetes due to its effect on insulin,” said Giovannucci, a senior researcher on the study. “So we hypothesized that we’d see a reduction in some cancers as well.”

For the study, researchers observed cumulative coffee intake in relation to endometrial cancer in 67,470 women who enrolled in the Nurses’ Health Study. Drinking more than four cups of coffee per day was linked with a 25 percent reduced risk for endometrial cancer. Drinking between two and three cups per day was linked with a 7 percent reduced risk. A similar link was seen in decaffeinated coffee, where drinking more than two cups per day was linked with a 22 percent reduced risk for endometrial cancer.

But keep in mind, that’s the relative risk. A woman has about a one in 37 lifetime risk of endometrial cancer, so a 25% reduction in risk would drop that to about one in 28.

One major limitation of the study: it was not randomized, and coffee drinkers may have other traits that affect their risk.

We asked Marji McCullough, ScD, RD, Strategic Director, Nutritional Epidemiology for her thoughts on the study.

“These results are intriguing, as the authors point out possible biological explanations. However, additional large studies are needed to further explore associations with dose, and in subgroups. For example, the association in never smokers was weaker. An association in never smokers would help pinpoint a specific role for coffee.

“If a woman drinks coffee currently, this may be one benefit. If not, there are other important ways to reduce the risk of endometrial cancer, such as maintaining a healthy body weight and staying physically active.”

For more about endometrial cancer, see the Detailed Guide on cancer.org.